Servomotor with piston operated locking means



Je L w48. ra. N. ASHTON SERVOMOTOR WITH PISTON OPERATED LOCKING MEANS Filed Feb. 14, 1946 Patented June 1, 1948 SERVOMOTOR WITH PIS'IOliI OPERATED LOCKING MEANS Benjamin N. Ashton, Kingston, N. Y., assignmt Electrol Incorporated, Kingston, N. Y., a corpo'- ration of Delaware Application February 14, 1946, Serial No. 647,484

Claims.

This invention relates to improved types o hydraulic jacks suitable for use in lifting and hoisting mechanisms, More particularly, the invention relates to an improved type of hydraulic Jack in which the piston can be locked at opposite ends of its stroke and which can be released either manually or by means of hydraulic pressure for movement to the opposite end of its stroke.

Many different types of hydraulic jacks have been manufactured heretofore for use in aircraft and the like for operating retractable landing gears, wing naps and the like.

for locking the piston to the cylinder of the jack at opposite ends of its stroke so that the jack can be operated only under the control of the operator.

It has been found that these locking types of jacks are not entirely satisfactory under all con- I ditions'of use. For example, when the hydraulic system'is damaged, the hydraulic iluid may be lost so that the jack cannot be released for extension or retraction'.

In my copending joint application, Serial No. 562,832, filed November 10, 1944, now Patent No. 2,434,828, a hydraulic jack is disclosed which is provided with a hydraulic lock-releasing mechanism and a manual lock release so that the piston can be unlocked to permit gravity or manual operation of the piston and the cylinder.

The present invention constitutes an improvement over the manual and hydraulic release system disclosed in application Serial No. 562,832.

In accordance with the present invention, I have provided a hydraulic jack that includes the usual cylinder, a piston reciprocable therein, and cooperating locking elements on the piston and the cylinder which may be actuated by locking pistons mounted in the ends of the cylinder to latch or lock the piston to the cylinder.

'I'he locking pistons are so arranged with respect to the reciprocating piston that upon application of fluid pressure to the cylinder at the end where the piston is locked, the locking ated to displace the locking pistons at both ends Some of thesehydraulic jacks are provided with mechanisms manually or under -the force of gravity for travel from one locked position toward the opposite end of the cylinder.

Inasmuch as the cylinder will normally contain iluid on one side of the piston, I have provided valve elements at both ends of the cylinder which also are actuated'by the manual operated members to permit the free ow of iluid .into and out of the cylinder on both sides of the operating piston. In 4this way, resistanceto movement oi the operatingpiston is reduced tol a minimum and the jack can be operated manually or by gravity with a minimum of resistance.

For a better understanding of the present invention, reference may be had to 'the accompanying drawing in which the single gure is a perpiston is displaced to release the operating piston.

of the cylinder simultaneously so that the operating piston can be released for movement spective view ol a typical form of hydraulic jack embodying the present invention shown partly in longitudinal section and partly broken away.

The form of hydraulic jack illustrated in the drawing is typicalvof the invention and, as illustrated,includes locking elements at both ends of the cylinder. It" will be understood, however. that in a lifting jack, one of the locking elements can be omitted if desired and only the locking element retained which holds the jack in retracted position. v

The form of jack illustrated includes a cylinder In which is provided with end closure caps I I and I2 at its opposite ends, these caps being arranged in huid-tight relationship to the cylinder It by means of threaded connections I3 'and I4 and suitable fluid-tight seals or packings I5 and I 6. The end closure II is provided with a lug I1 by means of which the cylinder I0 may be supported. The end closure cap I2 is provided with a packed bushing I84 which slidably receives the piston rod I 9. A'piston member 2l) is mounted on the inner end oi the piston rod I9 for reciprocation in the cylinder. The piston 20 may consist of a cylindrical member having a groove 2| in its periphery for receiving a toroidal rubbery ring 22 which acts as a piston ring to prevent leakage around the piston 20. One end of the piston 2li-is provided with an annular ilange 23 having aplurality of apertures. 2l therein for receiving a number of balls 25 that are used for locking the piston 2U at the left-hand end of its The other end of the piston is provided with' another ball-receiving iiange -21 receiving loosely a plurality of balls 2l which are adapted to lock 3 the piston 23 to the right-hand end oi the cylinder.

The balls 25 cooperate with a ring-like channel member 23 fixed within the left-hand end of the cylinder 24, while the balls 23 cooperate with a similar ring-like channel member 33 at the righthand end o! the cylinder. The balls are so arranged that they can pass by the flanges of the channel members 29 and 33 but are forced into these channels by means of the locking piston elements 3| and 32 which are slidably mounted in the caps |I and I2. Only one of the locking pistons 3| will be described inasmuch as the pistons 3| and 32 are similar.

The piston 3| is a generally cylindrical block of metal or other material having a reduced projecting end portion 33 of generally disk-like shape which is of suiilciently small diameter to be received within the flange 23 on the piston 23. The diameter of the projection 33 is such, however, that it cannot enter completely the flange 23 until the balls 25 are opposite the channel member 29. Then the locking piston 3| is forced to the right by means of the springs 34 which are interposed between the inner end of the closure II and the outer end of the piston 3|. When the piston 3| moves to the right. it forces the balls 25 outwardly in a radial direction into the channel member 29 and locks the piston to the cylinder. In order to release the piston 23 for movement to the right, the closure cap II is provided with a uid inlet port 35 which overlies an annular channel 33 formed in the periphery of the piston 3|. The channel 33 communicates with the space in which the balls 25 are received through a plurality of small passages 31 so that the piston 23 and the locking piston 3| .are subjected to fluid pressure, tending to urge them apart. Thus, when fluid under pressure is introduced through the port- 35, the locking piston 3| is urged to the left and the balls 25 are released for movement inwardly to unlock the Vpiston 23 and allow the fluid under pressure to push the piston 23 to the right. The piston 23 is locked at the end of its stroke to the right by the movement of the balls 23 partially in the channel 33 under the action of locking piston 32.

The balls 23 can be released from the channel 33 by introducing iluid under pressure into the cylinder through the port 33 in the end closure I2. Y

It is sometimes desirable to release the piston 23 for movement by gravity or manually from one end of the cylinder I3 to the other. In accordance with the present invention, the piston 23 can be released manually by means of the cam elements 43 and 4I which are mounted in the closure caps II and I2 respectively. The cam member 4 3 includes a generally cylindrical body portion 43a and enlarged cylindrical end portions 42 and 43 that are rotatably mounted in suitable openings 44 and 45 in the end closure cap II. The cam member 43 extends loosely through a transverse opening 43 in the piston 3| and is provided with flats or cam portions 41 and 43 about a 45 or slightly greater rotation of the cam 4|. The cam 41 is journaled in the end closure cap I2 and is provided with cam flats, not shown, which engage the piston 32 to urge it to the right. The cam 4| is also provided with a lever 53 which is connected by means of a link 54 to the lever 53 ofthe cam 43. Thus, when the link 54 is shifted, for example, to the left as viewed in the drawing, the cams 43 and 4| are rotated as to retract the locking pistons 3| and 32 and release the piston 23 for movement along the cylinder.

Inasmuch as the cylinder contains the fluid that moved the piston from one end of the cylinder to the other, such fluid restricts the free movement of the piston. Therefore, in order to facilitate the flow of liquid from and into the cylinder in accordance with the movement of the piston 23, I have provided each of the locking pistons 3| and 32 with uid release valves. Inasmuch as the valve structures in the pistons 3| and 32 are the same, only the valves in the piston 32 will be described in detail. Each of these valves includes a valve plug 55 which has a conical surface 56 thereon engaging a conical valve seat 51 in the piston 33. The valve plug 55 has a stem 53 which is disposed adjacent the at cam surfaces 53 carried on the cam member 4|. The valve seats -51 are located within the piston 32 about midway of the length of the passages 33 extending through the piston 32 and is at the junction of an enlarged section 33a and a reduced section 33h of the passage 33. The valve plug 55 is normally urged against the seat 51 by means of a coil spring 3| which is retained in the enlarged section 33a of the passages by means of the threaded retaining ring 32. The end closure cap I2 is provided with a relief port 33 which communicates with the interior of the cylinder I3 through the passage 33 in the piston 3|. The valve plugs 55 are so arranged that when the manually operated cams 4I and 42 are rotated to displace the locking pistons 3| and 32, the valve which engage the wall .43 bounding the opening drical portion 5I having an enlarged opening 52 therein through which the piston rod I3 passes. The opening 52 is suillciently large to permit plugs 55 in both of these pistons are unseated thereby permitting free flow of liquid between the interior of the cylinder I3 and the port 33 in the'cap I2 and the port 34 in the cap II which may, for example, be connected to the return line of a hydraulic system. Thus, when the link 54 is moved endwise, both of the locking pistons 3| and 32 are displaced outwardly and the valves therein are opened so that theplston 23 can be stroked easily by gravity or manually from one end of the piston to the other. The piston can be released also by hydraulic pressure applied through the port 35 or the port 33, depending upon the position of the piston 23.

From the preceding description of a typical form of hydraulic cylinder embodying the present invention, it will be apparent that the cylinder which has been provided may be actuated either hydraulically or manually. The piston is locked at each end of its stroke so as to prevent inadvertent extension or retraction of the piston rod due to failure of the hydraulic pressure. Nevertheless, the piston can be released manually and shifted from one end of the cylinder to the other manually or by gravity with little resistance from the hydraulic iluid present in the system.

It will be understood, of course, that the hydraulic jacks embodying the present invention are susceptible to considerable modification in.

described above should be considered as illustrative only of the invention and not as limiting the scope of the following claims.

I claim:

l. A hydraulic motor comprising a cylinder having closures at its ends, a piston reciprocable axially of said cylinder, means for supplying liquid to one end of said cylinder to move said piston toward the opposite end oi -said cylinder, movable locking means at said opposite end for releasably locking said piston for movement to said opposite end, manually operable means for moving said locking means to unlock said piston for movement toward said one end, iiuid discharge ports at both ends of said cylinder, normally closed valve means at both ends of said casing for preventing discharge of iiuid through said discharge ports, and means connected with said manually operable means for opening said valve means to permit the now of nuid through said ports upon operation oi said manually operable means to unlock said piston.

A hydraulic jack comprising a cylinder having closures at its ends, a piston reciprocable axially of said cylinder, means for supplying liquid 'to one end of said cylinder to move said piston toward the opposite end of said cylinder, movable locking means at said opposite end for locking said piston to said opposite end, means responsive 'to hydraulic pressure supplied to said opposite end for moving said locking means to unlock said piston, manually operable means for moving said locking means to unlock said piston, normally closed valve means at the ends of said cylinder, and means connected to said manually operable means for opening said valve means in response to operation oi said manually operable means to free the piston for reciprocation in said cylinder.

E. A hydraulic jack comprising a cylinder having closures at its opposite ends, a piston slidable axially of said cylinder, means for supplying iluid to opposite ends of said cylinder for reciprocating the piston therein, movable locking means at opposite ends of said cylinder for locking the piston to the ends of said cylinder, means responsive to hydraulic pressure for moving saidl locmng means to unlock said piston, manually operable means associated with said locking means for moving said locking means to unlock said piston, discharge passages at opposite ends ci said cylinder, normally closed valve means associated with said locking means and interposed between the interior of said cylinder andv said discharge passages, and means associated with said manually operated means for opening the valve means at both ends of said cylinder to prevent ow of liquid from and into opposite ends of said cylinder upon actuation of said manually operated means to unlock said piston.

4. A hydraulic jack comprising a cylinder having closures at its ends, a piston reciprocable axially of said cylinder, means for admitting fluid under pressure into opposite ends of said cylinder to reciprocate said piston, an internal recess adjacent each end of said cylinder, radially movable locking members carried by said piston and engageable in said recesses to lock said piston to' the ends of said cylinder, locking pistons movably mounted in the ends of said cylinder and engageable with said locking members to urge them into said recesses, said locking pistons being movable in response to iiuid pressure to release said locking members from said recesses, manually operable means for moving said locking pistons to release said locking members, valve means in said locking pistons, lsaid valve means being normally closed to prevent flow of uid through said locking pistons, and means connected to said manually operable means and operable therewith to open said valve means and allow the flow of iluid through said locking pistons when said manually operable means is operated to release said locking means.

5. A hydraulic jack comprising a cylinder having closures at its ends, a piston reciprocable axially of said cylinder, means for admitting iluid under pressure into opposite ends of said cylinder to reciprocate said piston, an internal recess adjacent each end of said cylinder, radially movable locking members carried by said piston and engageable in said recesses to lock said piston to the ends of said cylinder, locking pistons movably mounted in the ends of said cylinder and engage-A ablewithsaid locking members to urge them into said recesses, said locking pistons being movable in response to uid pressure to release said locking members from said recesses, interconnected manually operable cam means at opposite ends of said cylinder for moving said locking pistons to release said locking members, valve vmeans in said locking pistons, said valve means being normally closed to prevent the ow of iluid through said locking pistons, and means connected to said cam means and operable therewith to open said valve means and allow the now ofV fluid through both of said locking pistons when said cam means is operated to release said locking means.

BENJAMIN N. ASHTON.

REFERENCES CITED The following references are of record in the file of this patent:

Italy June 2v, 193s 

